It may be desirable to direct an air stream from a ventilation system toward a person in order to provide comfortable heating or cooling to the person. This may be more easily implemented when the person is in a known location, such as when seated in a vehicle cabin. This directed air stream is sometimes referred to as spot conditioning. As used herein, spot conditioning means directing a stream of air at a specific temperature and flow rate toward a thermally sensitive portion of a person's body to provide a heat supply rate to the sensitive portion that is equivalent to the heat loss rate at a comfortable temperature.
To provide a heat supply rate using a small air stream, such as an air stream typically used for spot conditioning, a higher velocity air stream may be desired to compensate for a smaller air stream volume. However, it has been observed that there is an upper limit on the velocity of the air stream contacting the person at which the person will feel comfortable, typically about 1 meter per second. Therefore, in order to provide a comfortable air stream, the air stream velocity may be controlled so that it provides the desired heat supply rate, but is limited to provide a conformable contact velocity. As used herein, the comfortable contact velocity is the maximum velocity for the air stream impinging on the body of a person at which the person would feel comfortable. It has also been observed that the velocity of an air stream varies in relation to the distance from the source of the air stream. Therefore, the distance between the air stream source and the person contacted by the air stream may need to be determined in order to provide a comfortable air stream contact velocity at the point at which the air stream contacts the person.